body {
  font-family: monospace;
  background-color: #111;
  color: #0f0;
  margin: 0;
  padding: 20px;
}
@media (prefers-color-scheme: light) {
  body {
    background-color: #f4f4f4;
    color: #333;
  }
}
header {
  background: #222;
  padding: 10px;
}
nav a {
  color: lime;
  margin: 10px;
  text-decoration: none;
}